The present invention relates to a steering system for vehicles and, in particular, to such a steering system having a telescopic operation.
A steering system of the type described above is disclosed in Japanese Patent Application No. 63-15299 (1988), filed by the applicant of the present invention. The prior art comprises a fixed bracket that is secured to a member on a vehicle body, a fixed shaft rotatably supported by the fixed bracket, a movable bracket connected for axial movement to the fixed bracket, a movable shaft connected to the fixed shaft in a manner to be axially movable relative to the axial shaft but rotatable with it as one unit, the movable shaft being rotatably supported by the movable bracket, and a driving mechanism disposed on the fixed bracket and connected to the movable bracket to move the movable bracket, together with the movable shaft, axially relative to both the fixed bracket and the fixed shaft. In this prior art, rigidity of the steering system is established by the frictional force that is generated at the joint of the fixed and movable brackets or the joint of the fixed and movable shafts. Accordingly, to enhance the rigidity of the steering system, it is necessary to increase the frictional force occurring between the fixed and movable brackets or between the fixed and movable shafts. However, if the frictional force is increased, the sliding resistance increases correspondingly, so that smooth sliding of the movable bracket and shaft is sacrificed. In addition, the size of the driving mechanism that causes the movable bracket and shaft to slide increases to be disadvantageous in terms of both space and cost.